1. Field of the Invention
The present invention relates to a locking device of an air-operated normally-closed valve for a gas cylinder. The preset invention further relates to such a locking device in which an indicating mechanism for indicating a valve opened state of the valve is incorporated.
2. Description of the Related Art
Gas cylinders having a high internal pressure (e.g., approximately over 200 kg/cm2) are generally provided on a valve port thereof with a manual valve or an air-operated normally-closed valve. If a large shock is accidentally given to the air-operated normally-closed valve during transportation and the like, there is a possibility of the air-operated normally-closed valve being opened momentarily since, generally, the air-operated normally-closed valve is closed by spring force. A conventional locking device of the air-operated normally-closed valve for a gas cylinder is used to exert a mechanical locking force on a valve body positioned inside the valve port of the gas cylinder to prevent the air-operated normally-closed valve from being opened accidentally during transportation.